Any of about 60–70 species of birds (family Caprimulgidae) found almost worldwide in temperate to tropical regions. The name is sometimes applied to all birds in the order Caprimulgiformes. (The name goatsucker derives from an old belief that they sucked goat's milk at night.) Nightjars are gray, brown, or reddish brown. They eat flying insects at night. The common nightjar (Caprimulgus europaeus) has a flat head; wide, bristle-fringed mouth; large eyes; and soft plumage that results in noiseless flight. It is about 12 in. (30 cm) long. Its North American relatives include the nighthawk and whippoorwill.
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Nightjars are medium-sized nocturnal or crepuscular birds with long wings, short legs and very short bills that usually nest on the ground. Nightjars are sometimes referred to as goatsuckers from the mistaken belief that they suck milk from goats (the Latin for goatsucker is Caprimulgus). Some North American species are named as nighthawks.
Nightjars are found around the world. They are mostly active in the late evening and early morning or at night, and feed predominantly on moths and other large flying insects.
Most have small feet, of little use for walking, and long pointed wings. Their soft plumage is cryptically coloured to resemble bark or leaves. Some species, unusually for birds, perch along a branch, rather than across it. This helps to conceal them during the day. Bracken is their preferred habitat.
The Common Poorwill, Phalaenoptilus nuttallii is unique as a bird that undergoes a form of hibernation, becoming torpid and with a much reduced body temperature for weeks or months, although other nightjars can enter a state of torpor for shorter periods.
Nightjars lay one or two patterned eggs directly onto bare ground. It has been suggested that nightjars will move their eggs and chicks from the nesting site in the event of danger by carrying them in their mouths. This suggestion has been repeated many times in ornithology books, but while this may accidentally happen, surveys of nightjar research have found very little evidence to support this idea.
Subsequent work, both morphological and genetic, has provided support for the separation of the typical and the eared-nightjars, and some authorities have adopted this Sibley-Ahlquist recommendation, and also the more far-reaching one to group all the owls (traditionally Strigiformes) together in the Caprimulgiformes. The listing below retains a more orthodox arrangement, but recognises the eared-nightjars as a separate group. For more detail and an alternative classification scheme, see Caprimulgiformes and Sibley-Ahlquist taxonomy.
Also see a list of nightjars, sortable by common and binomial names.